Engine cooling system thermostat bypass for dual temperature control

ABSTRACT

A dual temperature control system as part of an engine cooling system. In one aspect, a valve is regulated as a function of engine load and disposed in a by-pass line between the radiator and the coolant pump. The valve is designed to normally block the by-pass line, but permits coolant to by-pass the thermostat and be conveyed from the radiator to the engine when the load of the engine approaches a wide-open-throttle condition. In another aspect, both high-temperature and low-temperature thermostats are employed and a normally closed valve is actuated when the load of the engine approaches a wide-open-throttle condition to permit coolant to be conveyed through the low-temperature thermostat and on to the engine.

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] The invention relates to internal combustion engine cooling systems, and more particularly to dual temperature control arrangements for an engine cooling system.

[0002] In a typical liquid-cooled engine, the set-point of the coolant thermostat is the result of a compromise between lowered hydrocarbon emissions and improved fuel economy at part-load conditions that favor a higher temperature set point, and the best power available at Wide-Open-Throttle (hereinafter, “WOT”) that is benefited by a lower temperature set point. Currently, standard practice is to set the thermostat at a temperature between 190° F. and 200° F. Specifically, part-load fuel consumption and emissions are improved by operating the engine at 225° F. to 240° F., and peak power output can be enhanced by operating at tempertures as low as 160° F.

[0003] Higher coolant temperatures provide lower hydrocarbon emissions input because warmer combustion chamber surface and cylinder bore walls have thinner quench layers and therefore lower hydrocarbon production. This lower hydrocarbon production, along with friction reduction and lower throttle losses leads to better fuel consumption. WOT performance is enhanced at lower coolant temperatures because knock resistance is improved at lower combustion chamber, inlet port, and piston surface temperatures. Also, lower temperature intake ports can improve volumetric efficiency. Additionally, higher than normal coolant temperatures (above 210° F.) at WOT are not practical due to the associated reduction in knock resistance and hence power output.

[0004] Behr Thermot-tronik Co.'s “MAP Controlled Cooling System” accomplishes a dual thermostat setting by starting with a high-temperature (roughly 230° F.) thermostat that has a electric heating element in the wax “motor” of the thermostat. When electric current is applied to the heating element, the high-temperature thermostat is fooled into opening fully, thereby effectively lowering the set-point to a temperature that is more advantageous for best power. One disadvantage of this system is that it is relatively slow to react to the applied current as it takes roughly 4 seconds for the thermostat to fully open. Therefore, this system is inferior because transient power is reduced due to knock limitations and due to the significant calibration attention required by this system.

[0005] The foregoing demonstrates that there is a need for dual temperature control of an engine cooling system that optimizes hydrocarbon emissions, fuel economy, and power while providing quick response time such that transient power is sustained.

[0006] The invention satisfies the need and avoids the drawbacks of the prior art by providing an apparatus, system and method that efficiently provides dual temperature control of an engine cooling system. The invention also provides quicker response and lower cost compared to electronic thermostats. The invention further provides reduced pressure drop compared to an electronically-controlled thermostat, at high power settings, which may allow additional benefits with regard to coolant pump sizing.

[0007] Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 provides a schematic view of one embodiment of the system employing a dual thermostat feature according to the principles of the invention.

[0009]FIG. 2 provides a schematic view of another embodiment of the system utilizing an additional coolant circuit according to the principles of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0010] It is understood that the coolant circuits depicted in FIGS. 1 and 2 relate to only a portion of an internal combustion engine, which is of known design and function, and therefore the details of the operation are only briefly discussed. An internal combustion engine having a cylinder block 10 and a cylinder head 20 is connected to a coolant circuit. The coolant circuit has a coolant pump 30 which may be driven by the engine crankshaft. Located after cylinder head 20 in the coolant flow direction is a tee 40 that permits coolant to flow through a bypass line 50 to a thermostat or through a radiator inlet line 60 to a radiator 70.

[0011] As is shown in FIG. 1, in one embodiment according to the invention, radiator outlet line 80 permits coolant to flow from radiator 70 to a tee 90 which splits into a high-temperature thermostat inlet line 100 and a low-temperature thermostat line 110. High-temperature thermostat inlet line 100 permits coolant to flow to a high-temperature thermostat 120 and low-temperature thermostat line 110 permits coolant to flow to low-temperature thermostat 130 when valve 140 is in an open position. From high-temperature thermostat 120 and low-temperature thermostat 130 coolant flows through coolant pump inlet line 150 to coolant pump 30. Also bypass line 50 may be routed to flow over the temperature-sensing element of thermostat 120 and/or 130 if this is required to improve temperature regulation.

[0012]FIG. 2 illustrates a different embodiment, according to the invention, where coolant flowing through the radiator outlet line 80 flows from radiator 70 to a tee 90 which splits into a thermostat inlet line 200 and a by-pass inlet line 260. Coolant flows from thermostat inlet line 200 to thermostat 220 and to coolant pump 30 via coolant pump inlet line 250. Additionally, according to the principles of the invention, when valve 270 is open coolant flows from by-pass inlet line 260 to by-pass outlet line 280 and then to coolant pump 30 via coolant pump inlet line 250 and on to cylinder block 10 and cylinder head 20. Of course, the depicted arrangement of these devices and lines are illustrative and could be modified according to the principles of the invention. For example, the coolant pump may be located between the cylinder block/head and the radiator. The thermostats of the invention are depicted in a location at the pump inlet; however, the thermostats may be located at the engine outlet. Also bypass line 50 may be routed to flow over the temperature-sensing element of thermostat 220 if this is required to improve temperature regulation. A temperature monitor 160 is located between coolant pump 30 and cylinder block 10, but, of course, could be located in a variety of positions in the coolant circuit.

[0013] In one aspect, operation of the system accomplishes a dual temperature advantage, according to the principles of the invention, by employing valve 140 to direct coolant to the low-temperature thermostat 130 and on to the cylinder block 10 and cylinder head 20 to quickly cool the engine so as to improve peak power output. In a preferred embodiment, when the system is operating at part-throttle, valve 140 is closed and the temperature of the coolant is controlled by high-temperature thermostat 120. Valve 140 may be simple or complex and may be actuated using any number of mechanisms including electric, mechanical and vacuum. The lines used in the invention, such as line 110, may be hoses or any other fluid conveying devices and may be constructed of any suitable material acceptable for the temperatures, pressures, and service associated with coolant systems for engines. According to the principles of the invention, in order to take full advantage of the inventive system, high-temperature thermostat 120 may be designed to operate at a temperature that is significantly higher than is what is employed in current practice. For example, current systems that are controlled in a range of 195 to 200° F. may be modified to utilize thermostats having temperature set points in a range of 220 to 240° F. These higher temperatures are advantageous for reduced hydrocarbon emissions and enhanced fuel economy. During operation of the internal combustion engine associated with the coolant system of the invention, when power demand approaches or is at WOT, valve 140 will open to allow the coldest coolant in the system, coolant exiting radiator 70, to flow to low-temperature thermostat 130 and on to coolant pump 30, and at an increased flow rate due to reduced pressure drop, to rapidly lower the engine operating temperature. The lower engine operating temperature results in an improved peak power output at WOT.

[0014] In another aspect of the invention, described in connection with FIG. 2, operation of the system accomplishes a dual temperature advantage by providing a by-pass circuit around a themostat 220, as depicted in FIG. 2, via valve 270 and by-pass inlet line 260 to by-pass outlet line 280. Like valve 140, valve 270 may be simple or complex and may be actuated using any number of mechanisms including electric, mechanical and vacuum. Similarly as described above, lines 260 and 280 may be hoses or any other fluid conveying devices and may be constructed of any suitable material acceptable for the temperatures, pressures, and service associated with coolant systems for engines. In one preferred embodiment, when the system is operating at part-throttle, valve 270 is closed and the temperature of the coolant is controlled by thermostat 220, which is, according to the principles of the invention, set at a temperature that is significantly higher than is what is employed in current practice. For example, current systems that are controlled in a range of 195 to 200° F. may be modified to utilize thermostats having temperature set points in a range of 220 to 240° F. These higher temperatures are advantageous for reduced hydrocarbon emissions and enhanced fuel economy. During operation of an internal combustion engine associated with the coolant system of the invention, when power demand approaches or is at WOT, bypass valve 270 will open to allow the coldest coolant in the system, coolant exiting radiator 70, to flow into coolant pump 30 directly, and at an increased flow rate due to reduced pressure drop, and thereby rapidly lower the engine operating temperature. The lower engine operating temperature results in a desired peak power output at WOT.

[0015] In other embodiments, high-temperature thermostat 120 and thermostat 220 may have lower temperature set points than described above because suitable results may be obtained when the high-temperature thermostat 120 is set at a higher temperature than the low-temperature thermostat 130 with respect to the two thermostat system, and in the single thermostat system of the invention thermostat 220 should be set to provide the best part-throttle overall performance and reduction of emissions. For example, the thermostat may be set in a relatively low temperature range of 160 to 180° F. in a racing cooling system.

[0016] Valves 140 and 270 may be actuated in any number of manners. In one embodiment, the valve is a vacuum-actuated valve where low vacuum opens the valve and high vacuum closes the valve. The vacuum line may be connected from valve to the intake manifold plenum. Because the intake manifold plenum has very low vacuum when the operating engine is at or near WOT, its low vacuum opens valve 140 or 270. Such a construction is advantageous as no electronic controls are required.

[0017] In another embodiment, valves 140 or 270 may actuated using an electric solenoid valve. When the operating engine approaches or is at WOT, the valve is opened by a direct signal from an engine controller.

[0018] In still another embodiment, the disclosed valves may be vacuum-actuated where the vacuum signal to the valve is controlled by a vacuum switching valve (VSV) controlled by an engine controller. This alternative offers greater control than the vacuum-actuated valve described above, and may be more economical than an electric solenoid valve.

[0019] Because the opening of the valve 140 or 270, lowers the overall flow resistance of the cooling system by decreasing the flow resistance around the thermostat, cooling of the engine is improved by the resultant increase in cooling flow rate through the engine. The disclosed design may allow for downsizing of the coolant pump and associated equipment and operating savings.

EXAMPLE

[0020] A system according to the principles of the invention, and particularly the system depicted in FIG. 2, was constructed and tested on a 4.7 L V8 engine in a vehicle. The standard 195° F. thermostat was replaced with a 225° F. thermostat, and a vacuum-actuated coolant-control valve was attached between the radiator outlet hose and a fitting between the thermostat and the pump inlet in the front cover of the engine utilizing ⅝″ hose fittings. After the vehicle's engine was warmed up, a WOT condition was initiated and the temperature of the coolant conveyed through the by-pass circuit to the coolant pump was lowered by approximately 10° F. in 5 seconds, which is substantially faster than current systems.

[0021] Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims. 

What is claimed is:
 1. An apparatus for regulating a coolant circuit for an engine, the coolant circuit having a radiator, a thermostat, a coolant pump, and a first coolant circuit for coolant flowing through the radiator, thermostat, coolant pump, and engine, the radiator and engine having feed and discharge lines, the apparatus comprising: a second coolant circuit connecting the radiator discharge line to the engine feed line; and a valve regulated as a function of engine load and disposed in the second coolant circuit, the valve blocking the second coolant circuit under normal operation of the engine and permitting coolant to by-pass the thermostat and be conveyed from the radiator discharge line to the engine feed line when the engine load approaches a wide-open-throttle condition.
 2. The apparatus of claim 1, wherein the coolant pump has a feed and discharge line and is located upstream of the engine; and the second coolant circuit is connected from the radiator discharge line to the coolant pump feed line.
 3. The apparatus of claim 1, wherein the valve comprises an electronic actuation mechanism.
 4. The apparatus of claim 1, wherein the valve comprises a vacuum-actuation mechanism.
 5. The apparatus of claim 4, wherein the engine comprises an intake manifold plenum and further comprises a vacuum line, wherein the vacuum line is disposed between the intake manifold plenum and the vacuum-actuation mechanism.
 6. The apparatus of claim 4, further comprising a vacuum switching valve, wherein the vacuum switching valve is in fluid communication with the vacuum-actuation mechanism.
 7. An internal combustion engine, the engine having feed and discharge lines, comprising: a radiator for cooling the internal combustion engine, the radiator having feed and discharge lines; a coolant pump for pumping coolant; a thermostat for regulating the temperature of the coolant directed to the engine; a first coolant circuit for the coolant flowing through the radiator, the thermostat, the coolant pump, and the engine; a second coolant circuit connecting the radiator discharge line to the engine feed line; and a valve regulated as a function of engine load and disposed in the second coolant circuit, the valve blocking the second coolant circuit under normal operation of the engine and permitting coolant to by-pass the thermostat and be conveyed from the radiator discharge line to the engine feed line when the load of the engine approaches a wide-open-throttle condition.
 8. The engine of claim 7, wherein the coolant pump has a feed and discharge line and is located upstream of the engine; and the second coolant circuit is connected from the radiator discharge line to the coolant pump feed line.
 9. A method of regulating the temperature of an engine, comprising: circulating coolant between a radiator and the engine, regulating the temperature of the engine using a thermostat, by-passing the thermostat and delivering coolant to the engine when the engine load approaches a wide-open-throttle condition.
 10. The method of claim 9, wherein the delivery further comprises conveying coolant from the radiator to a coolant pump that transfers coolant to the engine.
 11. An apparatus for regulating a coolant circuit for an engine, the coolant circuit having a radiator, a first thermostat, a coolant pump, and a first coolant circuit for coolant flowing through the radiator, first thermostat, coolant pump, and engine, the radiator and engine having feed and discharge lines, the apparatus comprising: a second thermostat; a second coolant circuit connecting the radiator discharge line to the second thermostat to the engine feed line; and a valve regulated as a function of engine load and disposed in the second coolant circuit, the valve blocking the second coolant circuit under normal operation of the engine and permitting coolant to be conveyed from the radiator discharge line to the second thermostat and to the engine feed line when the load of the engine approaches a wide-open-throttle condition.
 12. The apparatus of claim 11, wherein the coolant pump has a feed and discharge line and is located upstream of the engine; and the second coolant circuit is connected from the radiator discharge line to the coolant pump feed line.
 13. An internal combustion engine, the engine having feed and discharge lines, comprising: a radiator for cooling the internal combustion engine, the radiator having feed and discharge lines; a coolant pump for pumping coolant; a first thermostat for regulating the temperature of the coolant directed to the engine; a first coolant circuit for the coolant flowing through the radiator, the first thermostat, the coolant pump, and the engine; a second thermostat for regulating the temperature of the coolant directed to the engine; a second coolant circuit connecting the radiator discharge line to the second thermostat to the engine feed line; and a valve regulated as a function of engine load and disposed in the second coolant circuit, the valve blocking the second coolant circuit under normal operation of the engine and permitting coolant to be conveyed from the radiator discharge line to the second thermostat and to the engine feed line when the load of the engine approaches a wide-open-throttle condition.
 14. The engine of claim 13, wherein the coolant pump has a feed and discharge line and is located upstream of the engine; and the second coolant circuit is connected from the radiator discharge line to the coolant pump feed line.
 15. A method of regulating the temperature of an engine, comprising: circulating coolant between a radiator and the engine, regulating the temperature of the engine using a first thermostat, and regulating the temperature of the engine using a second thermostat when the load of the engine approaches a wide-open-throttle condition.
 16. The method of claim 15, wherein the second thermostat has a setting of less than 190° F.
 17. The method of claim 15, wherein the regulating using a second thermostat further comprises delivering lower temperature coolant to the engine.
 18. The method of claim 15, wherein the regulating using a second thermostat further comprises conveying coolant to a coolant pump that transfers coolant to the engine. 